Measure the window’s width horizontally, spanning from the outer edge to the outer edge, at three points: the top, middle, and bottom. Then, round down to the nearest ⅛ of an inch.

Stack width refers to the extra width that extends beyond your window, ensuring the drapery panels do not obscure the window when open, while also creating the illusion of a larger window. We recommend a 10-inch stack width on each side if there’s enough space.